A food chain will be more advantageous in terms of energy if it has

According to the $10\%$ law of energy transfer in an ecosystem, only about $10\%$ of the organic matter (food energy) available at one trophic level is turned into biomass and made available to the next level of consumers. The remaining $90\%$ is lost as heat to the environment, used in digestion, respiration, growth, and reproduction. Therefore, a food chain with fewer trophic levels (such as $2$ trophic levels) experiences the least cumulative energy loss, leaving the maximum amount of usable energy for the final consumer. Thus, a shorter food chain is highly advantageous in terms of energy efficiency. Distractors B, C, and D represent food chains with $3$, $4$, and $5$ trophic levels respectively, where progressive energy loss at each step significantly reduces the final available energy.